1. Field of the Invention
The present invention relates to a magnetic tape apparatus and a method for producing the same. More particularly, the present invention is concerned with a magnetic tape apparatus for recording and/or reproducing information while sliding a magnetic tape against a drum or a guide, and a method for producing the apparatus.
2. Description of Related Art
In magnetic tape apparatuses, such as video tape recorder (VTR), desired information is recorded and/or reproduced in a state such that a magnetic tape is in sliding contact against a drum which having a magnetic head and a guide for guiding the magnetic tape.
FIG. 12 is a view showing the construction of a driving mechanism for magnetic tape in a rotary head type recording-reproducing apparatus which is one example of the magnetic tape apparatus. A magnetic tape 51 is in sliding contact against the individual circumferential surfaces of stationary guides 45, 46, rotary guides 47, 48, 49, 50, and a drum portion 40 which is constituted by a rotary drum 41 and a stationary drum 43, and a magnetic head 42 provided in the rotary drum 41 records and reproduces information on a recording layer formed on the magnetic tape 51.
The rotary drum 41 is rotatably supported with a shaft by the stationary drum 43 to form the drum portion 40. The magnetic tape 51 is designed so that the magnetic head 42 can follow a predetermined track in the magnetic tape 51. The magnetic tape 51 runs so that a lower edge 51b of the magnetic tape moves along a lead 44 formed in the stationary drum 43, controlling the position of the running magnetic tape. The rotary guides 47, 48, 49, 50 individually have a substantially cylindrical form having flanges formed at both ends, and control the vertical movement of the upper edge 51a and lower edge 51b of the magnetic tape 51 to prevent the magnetic tape 51 from shifting from the predetermined position.
FIG. 13 is a view showing a driving mechanism for magnetic tape in a stationary head type recording-reproducing apparatus which is one example of the magnetic tape apparatus. Like in the controlling of the position of the running magnetic tape 51 shown in FIG. 12, an upper edge 68a and a lower edge 68b of a magnetic tape 68 are controlled by flanges formed at rotary guides 62, 63, 64, 65, controlling the vertical movement of the magnetic tape 68 so that a magnetic head 61 follows a predetermined track in the magnetic tape 68. The rotary guides 62, 63, 64, 65 disposed on the front and back sides of a stationary drum 60 for supporting the magnetic head 61 control the position in the height direction so that the upper edge 68a and lower edge 68b of the magnetic tape 68 individually move along the flanges.
The rotary guides 47, 48, 62, 63 respectively control the positions of the upper edges 51a, 68a of the magnetic tapes 51, 68, and the rotary guides 49, 50, 64, 65 respectively control the positions of the lower edges 51b, 68b. For example, in the rotary head type recording-reproducing apparatus, the rotary guides 47, 48, 49, 50 are individually designed and arranged so that they are at a slight angle to the running direction of the magnetic tape 51 indicated by arrows shown in FIG. 14. As shown in FIG. 14A, the surface of the magnetic tape 51 slid against the rotary guide 47 receives a static frictional force, so that the magnetic tape 51 receives a force which spirally pushes the tape up from the circumferential surface of the rotary guide 47, but the position of the upper edge 51a of the magnetic tape 51 is controlled in the height direction by the upper flange 47a of the rotary guide 47. Further, as shown in FIG. 14B, the rotary guide 49 for controlling the position of the lower edge 51b in the height direction is arranged so that it leans in the opposite direction to the leaning direction of the rotary guide 47 with respect to the running direction of the magnetic tape 51 indicated by an arrow shown in the figure. The surface of the magnetic tape 51 slid against the rotary guide 49 receives a static frictional force, so that the magnetic tape 51 receives a force which spirally pushes the tape down from the circumferential surface of the rotary guide 49, but the position of the lower edge 51b of the magnetic tape 51 is controlled in the height direction by the lower flange 49b of the rotary guide 49. Similarly the above-described controlling of the vertical movement of the magnetic tape is carried out in the stationary head type recording-reproducing apparatus having the driving mechanism shown in FIG. 13, and the vertical movement of the magnetic tape 68 is controlled by the rotary guides 62, 63, 64, 65.
As described above with reference to FIGS. 12 to 14, when controlling the position of the magnetic tape in the height direction in the conventional rotary head type recording-reproducing apparatus and stationary head type recording-reproducing apparatus, as shown in FIGS. 14A and 14B, the upper edge 51a or lower edge) 51b of the magnetic tape 51 is pressed against the upper flanges or lower flanges provided at the individual rotary guides 47, 48, 49, 50 and receives a reaction force, so that the upper edge 51a or lower edge 51b is compressed. When the force exceeds the static frictional force that the magnetic tape 51 receives from the individual rotary guides 47, 48, 49, 50, the magnetic tape 51 is pushed back down or up, so that the compressive force exerted on the upper edge 51a or lower edge 51b is released.